The wretched wraith is a boss mob found within the Creeping Winter DLC of Minecraft Dungeons.

The wretched wraith was once a normal wraith that dwelled within the grand chamber of a lonely fortress located on the island where the Creeping Winter takes place. After the shattering of the orb of dominance, one of the the shards of the orb landed on the island. It was found by the wraith in the grand chamber. As a result of the shard’s corruption, the wraith became colder and more powerful. The wretched wraith gained abilities to proceed to cover the entire island in snow and a creeping winter that devastated the local villagers living on the once-prosperous island.

Here i leave the wiki of the mob: https://minecraft.fandom.com/wiki/Minecraft_Dungeons:Wretched_Wraith